Abstract
The myofibrillar fraction of rat heart homogenates possesses proteolytic activity with an alkaline pH optimum, similar to that reported in skeletal muscle. The specific activity of this "myofibrillar alkaline protease" ("MAP") increases progressively with age. Prolonged starvation and streptozotocin-induced diabetes mellitus, with their attendant cardiac atrophy, cause 25 to 30% increases in the specific activity of MAP. Thyroxine-induced cardiac hypertrophy is accompanied by a 20 to 45% decrease in MAP, which returns to normal during regression of hypertrophy after cessation of thyroid treatment. Isoproterenol-induced cardiomyopathy is accompanied by a progressive reduction in MAP to 80% of control during the first day after injection with a sustained reduction over the next week. These results indicate that a non-lysosomal proteolytic enzyme (or enzymes) is associated with the myofibrillar fraction of rat hearts; this enzyme system possesses maximum activity at an alkaline pH and may undergo significant changes during cardiac hypertrophy, atrophy, or injury.
Original language | English (US) |
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Pages (from-to) | 669-676 |
Number of pages | 8 |
Journal | Journal of Molecular and Cellular Cardiology |
Volume | 10 |
Issue number | 7 |
DOIs | |
State | Published - Jul 1978 |
Keywords
- Aging
- Cardiac atrophy
- Cardiac hypertrophy
- Cathepsin D
- Development
- Diabetes mellitus
- Isoproterenol
- Proteolytic enzymes
- Starvation
- Thyrotoxicosis
ASJC Scopus subject areas
- Molecular Biology
- Cardiology and Cardiovascular Medicine